Multilateration enhancements for noise and operations management

ABSTRACT

Multilateration techniques are used to provide accurate aircraft tracking data for aircraft on the ground and in the vicinity of an airport. From this data, aircraft noise and operations management may be enhanced. Aircraft noise may be calculated virtually using track data in real-time and provided to a user to determine noise violations. Tracking data may be used to control noise monitoring stations to gate out ambient noise. Aircraft emissions, both on the ground and in the air may be determined using tracking data. This and other data may be displayed in real time or generated in reports, and/or may be displayed on a website for viewing by airport operators and/or members of the public. The system may be readily installed in a compact package using a plurality of receivers and sensor packages located at shared wireless communication towers near an airport, and a central processing station located in or near the airport.

FIELD OF THE INVENTION

The present invention relates to enhancements in the use ofmultilateration in noise and operations management.

BACKGROUND OF THE INVENTION

In an article published in Airport Noise Report(www.airportnoisereport.com) in 2004, inventors Tom Breen and Alex Smithdiscuss how airport noise office needs are driven by technology andinnovation in the market. The article comments on upcoming years in theairport noise monitoring business and identies a number of positivetrends in the industry. The following paragraphs are an extract fromthat article.

“The aviation industry is rapidly progressing towards the nextgeneration of noise and operation monitoring systems (NOMS) as earlyadopters of the technology are gearing up for replacement of theirlegacy systems. Today's NOMS users are more sophisticated and aredemanding high-tech solutions to their problems. The industry hasresponded and we are starting to see more innovation in the marketplacewith the release of new systems and services and an increase in noiseand operations monitoring patents and intellectual property.

Once the domain of expensive UNIX workstations, the NOMS market is nowentirely focused on the personal computer, integration with desktopoffice software, and corporate networks. It is no longer satisfactoryfor isolated noise offices to produce weekly noise level reports onpaper, plot low resolution flight tracks on a crude base map three dayslater, and hand type noise complaints into a database from a telephoneanswering machine. The next generation NOMS user is demanding real-timehigh-fidelity aircraft tracking and identification systems, calibratedbase maps and geographic information systems, and Internet-basedcomplaint data entry systems that feed more data than ever before intothe NOMS while requiring less time from office staff.

These next generation systems are able process and provide significantlymore data at a lower cost than previous systems. The Internet hasrevolutionized the way Americans get information and this revolution hasnot been lost on the next generation NOMS users who expect the Internetto be an integral part of their next NOMS. Features such as automatedcomplaint entry systems based on Internet technology and Web-based noiseoffice information portals are two new product trends being described intechnical specifications being written today.

Another important development is the trend towards increasing datafidelity and availability in real time. The synthesis of new noisemonitoring technology, improved aircraft tracking techniques, and theincorporation of other important data sources such as Digital AutomatedTerminal Information System (D-ATIS), will provide noise offices withmore accurate information more quickly than previously thought possible.

Rannoch (Rannoch Corporation, Alexandria, Va., the assignee of thepresent application) has recently developed a unique capability toconverge D-ATIS and other operations data with NOMS data. The D-ATISdata contains information about current weather (METAR), runways in use,field conditions, and advisories (NOTAMs), allowing AirScene™ to achievethe next dimension of awareness in terms of the airport operatingconditions and flight conditions each flight experienced. Answers toquestions that arise about whether airfield conditions explain why anaircraft did not follow a particular procedure are now easily andautomatically explained by a report produced using Rannoch's AirScene™NOMS.

Another interesting enhancement to the AirScene™ product line that islikely to increase data fidelity is (Rannoch's) new fully-integrateddigital voice recorder. The AirScene™ voice recorder is fully integratedinto the AirScene™ system. The user simply clicks the flight track ofinterest, and the AirScene™ digital recorder immediately plays back theATC recordings made during that event. This automatic correlation of thedigital voice recordings with the flight tracks significantly reducesthe time and effort required to conduct this type of investigation.

The NOMS market is demanding innovative technological solutions andRannoch is responding. (Rannoch) has recently joined the prestigious FAACenter of Excellence Aircraft Noise and Aviation Emissions Mitigation,created to identify solutions for existing and anticipated aircraftnoise and emissions-related problems. Rannoch has also been awarded afive-year contract from the DOT's Volpe Center in Cambridge, Mass. Thiscontract will be used to fund projects including new systems forimproving aircraft tracking, surveillance, communications, air trafficmanagement, and new technologies for airport environmental monitoringsystems. These important research contracts ensure that Rannoch'sinternal product development is in lock step with current and futureindustry needs.

The fusion of automated data streams into the next generation noise andoperations monitoring systems allows a level of understanding andawareness not possible a few years ago. Noise office staff members, whoused to wait days for restricted-use flight tracks from the FAA, can nowaccess high fidelity tracking information in real-time usingtechnologies, which just a few years ago, were restricted to themilitary and air traffic control industry. Given the current rate ofadvancement and innovation we are seeing the noise and operationsmonitoring business, the presence of new aggressive vendors, andresurgence of the American aviation industry, the rate at which the NOMSbusiness is changing is likely to continue accelerating over the nextfew years.”

The above excerpt from the Airport Noise Report article outlines some ofthe innovations set forth in the parent applications of the presentPatent Application, in particular, U.S. Patent Provisional ApplicationSer. No. 60/440,618 filed on Jan. 17, 2003, and corresponding U.S.patent application Ser. No. 10/751,115, filed on Jan. 5, 2004, entitled“Method and Apparatus to Correlate Aircraft Flight Tracks and Eventswith Relevant Airport Operations Information” (Alexander E. Smith etal.), both of which are incorporated herein by reference. These parentPatent Applications describe how airport operations and noise monitoringmay be automated using multilateration and data fusion techniques. Thefollowing paragraphs describe the background of the application ofMultilateration into the Noise Industry.

Multilateration has become extremely popular for aircraft tracking inthe past several years. The majority of all U.S. Noise and OperationsMonitoring (NOMS) contracts in recent years use multilateration as thesurveillance source. Multilateration offers tracking capabilities notavailable from any other techniques or systems, and is particularlyuseful for tracking aircraft at low flight levels and on surface areas.The following review of different multilateration systems is based onpublicly available information, which is believed to be correct, butreaders are advised to make their own assessment. Most of the technicalinformation provided herein is supplied from the various vendor websites(e.g., sensis.com, era.cz, and roke.co.uk, all three of which areincorporated herein by reference) and various publicly available sourcesincluding a November 2004 report NLR-CR-2004-472, entitled Wide AreaMultilateration, Report on EATMP TRS 131/04, Version 1.0, by W. H. L.Neven (NLR), T. J. Quilter (RMR), R. Weedon (RMR), and R. A. Hogendoorn(HITT), also incorporated herein by reference.

Because of the significant investment in science and engineeringrequired to successfully commercialize and produce multilaterationproducts, there are only three or four companies in the world thatproduce multilateration systems. Additionally, one or two other largeair traffic control systems providers claim to be testing prototypesystems or to have multilateration systems in development. For example,Siemens Roke Manor has deployed systems used for height monitoring andhas stated on their website other potential applications including widearea tracking.

Companies that have actually fielded a wide area multilateration systeminclude Sensis Corporation, ERA, and Rannoch Corporation. Sensis is aU.S. company whose clients are mainly FAA and other aviationauthorities. ERA is a Czech Republic company and has several Europeanaviation authority clients. Rannoch (assignee of the presentapplication) is a U.S. company whose clients include FAA, NASA, andseveral airport authorities. Each company uses the same general conceptof time difference of arrival (TDOA) measurement for multilateration.However, the methods and system architectures used by each company arevery different. Each company uses remote receiver stations and a centralprocessing system or central server. One of the key requirements forTDOA measurement is accurate time-stamping of received aircrafttransponder signals. The accuracy of the time-stamping is essentiallythe synchronization of the system and it must be performed to within afew nanoseconds (a few billionths of a second) in order to achieveaccurate tracking results.

There are three different methods in use currently to performsynchronization. Sensis Corporation uses a reference transpondertechnique. This approach places a fixed transmitter or set oftransmitters around the airport. The transmitters emit a transpondersignal, just like aircraft, but from a fixed location. The system thenuses these special transponder signals as a time reference (hence theterm reference transponder) and then all other received transpondersignals are timed relative to the reference.

The technique works well but has two main disadvantages. The first isthat the system generates it own transmissions on the 1090 MHz radarfrequency and the transmitters need line-of-sight to the receiverstations. In the U.S., the FAA will not allow this approach to be usedfor anything other than air traffic control (ATC) or Federal Governmentprograms, as it uses some of the available capacity of FAA's radarfrequency spectrum. Antennas used by Sensis for this technique, areillustrated in FIG. 1. These antennas are rather large and bulky, and asline-of-sight antennas, may need to be properly oriented. Approximately35 airports in the U.S. are slated to receive a Sensis ASDE-Xmultilateration system sometime over the next 10 years.

A second approach is the central timing technique as used by ERA. Thisapproach relies on the central processor to perform all of the timingfrom a single accurate clock source. Receivers placed around the airportdo not perform time-stamping, they merely receive the aircraft'stransponder signal, up-convert the frequency of the signal, and transmitit to the central server. There is no time-stamping or digitizing of thesignal at the receivers, they merely convert and re-transmit thereceived transponder signal. Since there is no digitizing or processing,there is a known fixed time delay in the conversion and re-transmissionprocess. All of the time-stamping and digitizing can then be performedat the central server using one clock source.

This second technique has significant disadvantages. A high-bandwidth,high power microwave links are needed between each receiver and thecentral station, as shown in FIGS. 2A and 2B. FIG. 2A shows the separatehigh power antennas used by the airport central station, one for eachreceiver. FIG. 2B shows the high power transmitter used for eachreceiving station. As can be clearly seen in the illustrations, theseantennas are even larger and bulkier than those of FIG. 1. In addition,as line-of-sight antennas, they require careful orientation. Suchantennas are fairly expensive as well. While this second technique hasbeen approved at some airports in Eastern and Western Europe, the FAAhas not approved it for use in the United States, nor is it anticipatedthat the FAA will approve it in the future, due to concerns with usingadditional radio frequency (RF) signals within the boundaries of anairport, which may cause interference.

The manufacturer's recommended datalink frequency range is in the 10-30GHz bands, the recommended minimum bandwidth is 28 MHz, and the datalinkpower ranges from 10s to 100s of Watts. The FAA is traditionally one ofthe strictest aviation authorities in terms of granting approval forradio frequency transmissions at airports. If a system is proposed forother than air traffic control applications and requires transmissionsoutside of approved commercial frequency bands (such as the digital WiFi802.11 standards) it has not traditionally received approval in theUnited States.

A third technique is the satellite timing technique as used by RannochCorporation, assignee of the present application. This third techniqueuses satellite timing at each receiver to time-stamp receivedtransponder signals. There are several satellite systems availableincluding the U.S. Global Positioning System (GPS). The RannochAirScene™ system uses a patented (U.S. Pat. No. 6,049,304, incorporatedherein by reference) technique for satellite synchronization, which isaccurate to a few nanoseconds. In addition, the system offers advantagesin equipment installation, as no line-of-sight is needed betweenreceivers and the central station. Most importantly, there is no need totransmit any signals whatsoever, as data from receivers can be sent to acentral station via non-radio techniques (e.g., hardwire, internet,local network, or the like). FIG. 3 illustrates one of Rannoch'sreceiver units combined with weather instrumentation into a compactinstallation package. From left to the right the items are: GPS,rainfall device, pressure device, wind speed and direction unit, andradar receiver unit. Note there are no transmitters in this package, andthus no additional RF signals are generated. Thus, FAA approval may notbe required for such an installation. As illustrated in FIG. 3, theantenna installation of this third technique is much more compact, lessexpensive, and less obtrusive than the installations of the first twotechniques as illustrated by FIGS. 1, 2A, and 2B.

A fourth technique is a height monitoring multilateration used bySiemens Roke Manor Research. Siemens was one of the pioneers ofmultilateration to determine aircraft height (i.e., altitude) for thereduced vertical separation program. Working with various governmentsand industry partners, Siemens deployed a handful of these sophisticatedheight measurement units. The company is believed to be embarking on anambitious development program to apply this technology to commercialwide-area tracking.

The original height measuring devices used components and subsystemsfrom many different suppliers, which made the overall systems veryexpensive. The systems were priced in the region of $10M USD each. As ofOctober 2005, there are no known mature operational Siemens systems usedfor airport tracking applications such as NOMS. In mid 2005, in anindependent assessment of the operational maturity of multilaterationtechnologies, the German government (DFS) found only four companies tobe qualified (Sensis, Rannoch, ERA, and Thales). Other systems,including the Siemens Roke Manor system, were not qualified by DFS asoperationally mature at that time for airport tracking applications.

The different multilateration techniques are summarized in Table 1.Table 1 includes a column titled “active system.” An active system isdefined as one that needs to interrogate each aircraft to elicit atransponder reply. Of the four, only the Sensis system needs tointerrogate aircraft, which is fundamental to the design of that system.The ERA and Rannoch systems do not need to generate interrogationsignals as they both are designed to handle most aircraft transponderreplies to a variety of other sources, such as ground radar or aircraftcollision avoidance devices. Therefore, both the ERA and Rannoch systemscan be classified as “passive” within the traditional definition of“active” and “passive.”

However, this classification does not mean that all passive systems donot use radio frequency transmissions for some functions; it means onlythat the passive system does not interrogate aircraft transponders. Asnoted previously, the ERA “passive” system needs a high bandwidthmicrowave link (as illustrated in FIGS. 2A and 2B) and therefore musttransmit high power signals constantly in airport environments, which isstrictly prohibited at U.S. airports. The “passive” Rannoch system, onthe other hand, does not transmit on any frequency for any purpose, andis used by the U.S. Federal Government for several monitoring projectsand is authorized for non-air traffic control purposes, such as noisemonitoring, at U.S. airports. Thus, as illustrated in Table 1, of thefour multilateration systems available, only one, the Rannoch system, istruly passive, does not require generation of radio transmissions, andhas been successfully implemented for airport noise and operationsmonitoring.

FIG. 4 illustrates an example of a real-time Rannoch AirScene™ display(in this example, from Louisville) and illustrates the ability of thesystem to provide data parameters from multiple AirScene™ sources inreal time. In the example of FIG. 4, data blocks selected by the userfor display include Mode A code (squawk), flight number (call sign),tail number, aircraft type, Mode C altitude, flight level, and originand destination. AirScene™ can supply or use any of these data sources.The example shown is unique to AirScene™, as no other NFTMS can displayall of the information as shown in real time. Other vendor approachesrequire extensive post-processing to match up the tail number with allof the other data.

FIG. 5 illustrates the same system when the operator queries aparticular aircraft by highlighting it (UPS 6058 on the top right). Allof the associated identification data is shown in the hyper-box on theright. When using AirScene™ multilateration tracking, runway utilizationis very accurate, as the system will usually track the departureaccelerating along the surface through rotation and departure. In thetwo examples of FIGS. 4 and 5, the user has selected all of the colors,icons, and GIS layers, including the 5 NM range rings shown.

As noted previously, the FAA is implementing an ASDE-X MultilaterationProgram in as many as 35 airports in the next 10 years in the UnitedStates. Many airport managers and operators have questions regarding theapplication of the ASDE-X program to commercial tracking applications.The following is an overview of the ASDE-X program and answers tofrequently asked questions regarding that program.

The Airport Surface Detection Equipment-Model X (ASDE-X) program wasinitiated in 1999 and Sensis Corporation was selected as the vendor inthe year 2000. The Senate Committee on Appropriations, in its report onFAA's fiscal year (FY) 2006 appropriations, expressed concern about thepace of ASDE-X deployment and reported that the FAA has not yet deployedsystems to more than half of the planned sites due to changes in systemdesign and additional requirements. The FAA originally planned tocomplete ASDE-X deployment to second-tier airports (e.g., OrlandoInternational Airport and Milwaukee General Mitchell InternationalAirport) by FY 2007 as a low-cost alternative to Airport SurfaceDetection Equipment-3 (ASDE-3) radar systems, which are deployed atlarger, high-volume airports. However, the FAA now plans to completedeployment by FY 2009, resulting in a two year delay. While FAA hasalready procured 36 out of 38 ASDE-X systems, only three systems havebeen commissioned for operational use as of late 2005. FAA has investedabout $250 million in ASDE-X and expects to spend a total of $505million to complete the program. (See, e.g., www.faa.gov). A map ofplanned ASDE-X installations (from www.asdex.net, incorporated herein byreference) as well as upgrades to the older ASDE-3 systems isillustrated in FIG. 6.

One question airport operators have is that if the FAA plans to installASDE-X at their airport, what additional benefits, if any, would beprovided by an AirScene™ system? The answer is that airports should beaware of realistic dates to receive an ASDE-X system, based on thedelays and cost overruns associated with program. Once installed, theASDE-X will provide coverage only on the movement areas, not in theterminal area, on the ramps, aprons, or to the gates. Furthermore, theASDE-X system is an FAA system and airport access to the data is notguaranteed on an unrestricted or even on a restricted basis.

Thus, a number of ASDE-X airports have contracted for and are currentlyusing an AirScene™ tracking system. These airports include T. F. GreenState Airport, Providence, R.I., San Antonio International Airport,Tex., and Raleigh Durham International Airport, N.C. Several more ASDE-Xairports are currently in contract negotiations and discussions for anAirScene™ system.

Another question airport operators ask is if their airport is receivingan ASDE-X system for the runways and taxiways (movement areas) would itjust be a small incremental cost to add coverage at the gates, ramps,and aprons? While it would seem logical that the costs would beincremental, based on experiences at several airports, the cost ofadding to a planned ASDE-X installation can be significantly higher thanthe installation of a complete stand-alone AirScene™ airport managementsystem. Furthermore, adding onto an ASDE-X installation ties the programschedule to the FAA's schedule and involves the FAA directly in theairport's program. As a stand-alone system, the Rannoch AirScene™ doesnot require regulation, intervention, monitoring or interaction with theFAA or Air Traffic Control systems. Thus, an airport manager or operatorcan implement and operate the Rannoch AirScene™ system without having toobtain permission from the FAA and without government interference.

Another question is whether the ASDE-X system affects the performance ofthe AirScene™ system and/or whether the AirScene™ system affects theASDE-X system. As noted above, the Rannoch AirScene™ system is a trulypassive system. Thus, there are no detrimental effects to either systemwhen they are both operational at the same airport. On the contrary, thepresence of an ASDE-X system generates more transponder replies for theAirScene™ system to detect and build aircraft tracks. Since AirScene™ isa passive system; it causes no interference to the ASDE-X systemwhatsoever.

Another concern of airport operators is that is seems that there is alot of work involved in finding sensor sites for ASDE-X sensors, andarranging telecommunications, particularly when some of the sites arelocated off airfield. AirScene™, however, uses small compact sensors andantenna (See, e.g., FIG. 3), which can be located virtually anywhere(on-site or off-site), and the communications are flexible, ranging fromtelephone lines, to TCP/IP, or other industry standard forms ofcommunication. Off-airport sites pose a significant challenge for ASDE-Xdue to problems with eminent domain, lease arrangements, and physicalsiting constraints due to the need for all ASDE-X sensors to haveline-of-sight to the airport.

In contrast, AirScene™ sensors do not need line-of-sight to the airportand are so small that they can be mounted atop shared wirelesscommunication towers. Through a contract with cell providers, AirScene™has access to over 20,000 towers across the country. Therefore, thereare few, if any issues of eminent domain, leasing, or siting with anAirScene™ system. Table 2 illustrates a comparison summary betweenASDE-X and the AirScene™ system. As illustrated in Table 2, only theAirScene™ system presently provides a practical system for airportmanagement.

From the foregoing description, it is quite clear that the onlypractical system for airport NOMS presently available is the RannochAirScene™ system. However, airports are becoming increasingly complex asa result of increased security concerns, increased traffic flow, costreduction pressures, and the like. As a result, it is desirable toexpand the capabilities and further enhance the AirScene™ system toprovide additional features, which are of use to airport managers andoperators in both the day to day operations of an airport, as well as infuture planning and management. The present invention incorporates theseimprovements to the Rannoch AirScene™ NOMS.

SUMMARY OF THE INVENTION

The present invention provides a number of embodiments wherebymultilateration techniques may be enhanced to provide additional orenhanced data and/or services for airport users, operators and otherparties.

In one embodiment, multilateration data may be used for NOMSapplications and may determine aircraft noise levels, either virtually,or combined with actual noise level measurements, and display such datain real-time or in response to queries from users. Such data may also bedisplayed on a website for designated users and/or members of the publicor other individuals. Such a website may allow users to monitor noiselevels and/or allow users or members of the public to enter noisecomplaints and the like. Virtual noise levels may be determined byknowing aircraft track (e.g., flight path, rate of climb, and the like)and type, as well as takeoff weight, fuel aboard, souls on board, andthe like. From this data, noise levels can be accurately inferred basedupon aircraft type and engine type. Noise levels from idling and taxiingcan also be determined from ground track data obtained throughmultilateration.

Multilateration may also be used to enhance the placement of noisemonitors in the community. Virtual noise calculations may besupplemented by actual noise monitoring stations (e.g., microphones)placed throughout a community. However, multilateration may allow fortracking of flight paths and provide a better model for placing suchnoise monitoring equipment. Thus noise monitors can be scientificallyplaced, rather than placed as based upon guesswork, political influence,or the like.

Once placed, multilateration can be used in real-time to trigger or“gate” signals from noise monitoring equipment, such that noise levelsare measured only during periods were flights are nearby. Most noisemonitoring equipment is indiscriminate with regard to type of noiserecorded. Thus, if loud ambient noise from construction equipment,motorcycle or car, yard equipment (e.g., leaf blower or the like) occursnear the noise monitoring equipment, it may be reported as a falsepositive for a noise violation, even if no aircraft is nearby. By usingaircraft tracking information in real-time, noise monitoring equipmentmay be monitored only when aircraft are in the immediate vicinity, thuseliminating false noise reports.

In another embodiment, aircraft emissions levels can be determined in asimilar manner. Since emissions are a function of engine type andthrust, emissions can be virtually determined by measuring the load onthe engine (based upon aircraft takeoff weight and climb profile) andknowing the type of engine on the aircraft. Aircraft identifyinginformation can be used to access databases indicating aircraft type andengine type. In addition, the amount of time spent by an aircraft at theairport idling or taxiing can be determined by track data, such thatemissions generated on the ground can be accurately calculated.

In a another embodiment, aircraft tracks are generated usingmultilateration systems independent of air traffic control radar, andare made available in real-time to noise monitoring personnel. Aircrafttracking data can then be correlated to measured noise level data todetermine whether a noise violation has occurred or is in the processingoccurring. If a noise violation is in the process of occurring, a pilotor other use can be warned of such an event, and can take effectiveaction (e.g., reduce rate of climb, thrust, flight path, or the like) toalleviate noise levels. Noise violation information can be transmittedto a pilot or other user using audio radio signals, visual displays,recorded messages, or the like.

In another embodiment, multilateration is used to provide tracking andother data to operate airport websites, providing aircraft informationfor airport users and the general public. Such data can be used fornoise monitoring websites, to elicit noise complaints from the publicand assist the public and airport users in understanding noise problems.Members of the public and airport users may use such websites todetermine whether a particular flight has arrived or departed, and wherein the airspace or on the ground, a particular aircraft is located.

The entire system may be installed readily as a matrix of sensorpackages installed on nearby shared wireless communication towers, alongwith a central station located in or near the airport. The sensorpackages may include multilateration receivers for receiving radiosignals from an airplane for use in determining aircraft position usingmultilateration techniques. The sensor packagers may also includephysical noise and emissions monitors. The central station may receivesignals from the sensor packages and generate detailed informationregarding noise levels and emissions levels caused by aircraft. The useof this packaged approach reduces complexity and cost and eliminates theneed for separate noise monitoring sensors and multilateration sensors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates examples of antennas used by Sensis for an aircrafttracking system 1.

FIG. 2A illustrates a high-bandwidth, high power microwave link antennaused by the airport central station, one for each receiver in the ERAsystem.

FIG. 2B illustrates the high power transmitter used for each receivingstation, in the ERA system.

FIG. 3 illustrates one of Rannoch's receiver units combined with weatherinstrumentation into a compact installation package.

FIG. 4 illustrates an example of a real-time Rannoch AirScene™ display(in this example, from Louisville) and illustrates the ability of thesystem to provide data parameters from multiple AirScene™ sources inreal time.

FIG. 5 illustrates the same system when the operator queries aparticular aircraft by highlighting it.

FIG. 6 illustrates a map of planned ASDE-X installations as well asupgrades to the older ASDE-3 systems.

FIG. 7 illustrates a schematic for the AirScene™ system where the datasources are shown at the top.

FIG. 8 illustrates examples of traditional-style website usingnear-real-time tracking of aircraft using their Mode A/C codes.

FIG. 9 illustrates an example of an airport websites using a timed delayof Government radar.

FIG. 10 is a block diagram illustrating the relationship betweendifferent embodiments of the present invention.

Table 1 summarizes the different multilateration techniques in usetoday.

Table 2 illustrates a comparison summary between ASDE-X and theAirScene™ system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is now described with reference to the Figureswhere like reference numbers denote like elements or steps in theprocess.

FIG. 7 illustrates a schematic for the AirScene™ system where the datasources are shown at the top. These various sources may or may not beavailable in all systems, but would be used if they were available at agiven airport.

Referring to FIG. 7, the system draws on data from the data sources 710,712, 714, 716, and 718. These data sources may include OperationalDatabases 710. Operational Databases 710 may include the OfficialAirline Guides (OAG) databases, SSID (Supplemental Structural InspectionDocument), the ASQP system, the FAA CATER (Collection and Analysis ofTerminal Records) system, FAA Flight Strips, and Aircraft RegistrationDatabase. Resultant data 720 from Operational Databases 710 may includeairline flight schedules, future anticipated operations, ownerinformation, aircraft movement records, and the like.

Databases 712 may include Flight Information and may include AircraftCommunication Addressing and Reporting Systems (ACARS) data, AircraftSituation Display to Industry (ASDI), Automatic DependentSurveillance-Broadcast (ASD-B), Controller-Pilot Datalink Communication(CPDLC), Mode-S transponder data, and the like. This data generated fromaircraft by radio signals may include relevant data 722 such as aircrafttype and weight, cargo, fuel weight, time on gate, off gate, on wheels,off wheels, air traffic controller (ATC) communication recording, andthe like. From this data, it is possible to determine aircraft weight,type, number of passengers, and other data relevant to airport revenuemanagement. For example, number of passengers on each airplane can becollected to determine total number of enplanements for the airport.

Databases 714 may include Airport Data Sources, including Common UseTerminal Equipment (CUTE), Local Departure Control System (LDCS), (See,http://www.damarel.com/products, incorporated herein by reference)Property/lease management systems, Geographic Information Systems (GIS),Computer Aided Design (CAD) data of airport terminals and facilities,Noise and Operations Monitoring System (NOMS), and the like. Databases714 may produce data 724 such as gates used, time on gate, off gate,passenger counts, revenue passengers, property and concession revenues,resource tracking, noise levels, and aircraft service records. Thisairport information, for example, when correlated with other data, suchas aircraft tracking data, can indicate which gate an aircraft is parkedat, which runways were used, and the like.

Aircraft Multilateration Flight Tracking Systems 716 may comprise, forexample, Rannoch Corporation's AirScene™ Mlat (multilateration) system,which is capable of identifying and tracking aircraft both in the airand on the ground using multilateration of radio signals. Other aircrafttracking systems may also be used, including aircraft sensors mounted intaxiways and runways (e.g. conductive loops or the like) or other typesof systems. Examples of such systems includes various models of AirportSurface Detection Equipment (ASDE), such as ASDE-X (see www.asdex.net,incorporated herein by reference), ASDE-3, and ASDE, as well as AirportMovement Area Safety System (AMASS), SITA Information NetworkingComputing (SITA INC), Short Messaging Service (SMS) (See,http://www.sita.aero/default.htm, incorporated herein by reference), theaforementioned ADS-B, and the like. Data 726 from such systems canproduce actual aircraft positions or tracks (paths followed). Positionand speed of aircraft can also be determined from such data. Inaddition, data 736 may include flight corridors, runways, taxiways, andgates used by aircraft, as determined from vehicle ground track,position and speed, along with other aircraft information andcommunications.

Other data sources 718 may describe airport conditions and may includedigital D-ATIS (Digital Automatic Terminal Information Service, see,http://www.arinc.com/products/voice_data_comm/d_atis/, incorporatedherein by reference), Automated Surface Observation System (ASOS), METAR(Aviation Routine Weather Reports, available from the FAA and othersources), TAF (Terminal Aerodrome Forecast) the aforementioned SMS,Internet weather sources, and the like. These sources may produce data728 indicating which runways are preferred, meteorological data, surfaceconditions, precipitation,/icing, coefficients of friction, and thelike.

Note that all of the data sources 710, 712, 714, 716, and 718 do notneed to be used in order to produce a satisfactory NOMS system. Some orall of these sources may be used, and/or additional sources of relevantdata may also be applied. Each source of data may generate data, whichmay be relevant to airport revenue or expenses. Missing data may befilled in by other sources. In addition, data from different sources maybe used to correlate data to increase accuracy of data reporting.

All of the available data 720, 722, 724, 726, and 728 may be provided toa NOMS database 730, called a “smart database” which is then availableto support the NOMS software 740, which is used to process theinformation. From the NOMS software 740 via the internet, intranet, orfrom PC Clients on the airport network a large variety of users 750 canrun reports and perform other airport operations.

In a first embodiment of the present invention, multilateration is usedto provide more extensive flight tracking and aircraft identificationthan other passive Radar tracking technologies. Passive trackingtechniques have been available for over 20 years. Megadata's Passur(www.passur.com, incorporated herein by reference) is installed at manyairports, while a newer version called SkyTrak is marketed by LochardCorporation (www.lochard.com, incorporated herein by reference) and isinstalled at a few airports. Both of these systems rely on the presenceof conventional radar for coverage, so they cannot provide coverage whenthere is no existing radar coverage.

Since these techniques rely on existing radar systems for tracking, boththe type of radar, and its configuration, may limit performance. Forexample, for a recent NOMS deployment in Boca Raton, Fla., the airportselected Lochard Corporation using a SkyTrak passive aircraft-trackingdevice. There were many requirements identified in the Boca RFP for theflight tracking system including Section 2-1.1.1, on page II-3,requiring reports that use an aircraft's start of take off roll, whichis only possible with a flight tracking system that has good low-levelcoverage at the airport.

The intention of the SkyTrak's passive technology was to provide theextreme accuracy required for close-in applications. Yet, based on BocaAirport Authority meetings, the SkyTrak did not perform and is no longerinstalled, nor operating at the airport. In the August 2005 minutes of ameeting of the Airport Authority, the authority voted on and approvedthe implementation of an FAA radar interface for the airport's noise andoperations monitoring system. The minutes are located athttp://www.bocaairport.com/pdf/min-authority/8-05MN.pdf, and areincorporated herein by reference.

Multilateration, on the other hand, has been demonstrated to drive NOMSat large and small airports with good low-level coverage throughout theUnited States and overseas. NOMS systems using multilateration includeCincinnati Lunken Municipal, Ohio, Providence, R.I., Indianapolis, Ind.,Louisville, Ky., and San Antonio, Tex. In the present invention,multilateration is used to track aircraft Noise and OperationsMonitoring (NOMS) as well as secondary applications, such as providingaircraft tracking data to airport website or the like. Themultilateration system of the present invention does not rely uponradar, and thus can be installed without FAA certification, approval, orother regulation. Since the system is passive, no licensing from the FCCis required for radio transmissions. Existing signals from aircraft arereceived by a plurality of receivers, which may be located on-site oroff-site. The use of off-site receivers is particularly useful insituations where airport authorities may resist the installation of asystem, which may be perceived as competing with existing, moreexpensive hardware.

In a second embodiment of the present invention, multilateration is usedto overcome traditional constraints regarding placement of monitors fornoise measurement throughout the community. Placement of noise monitorsaround airports has not been an exact science. Oftentimes monitors areplaced within political boundaries, or in certain people's back yards,without any real scientific reason. For example, for a Part 150 Studyfor Seattle/Tacoma airport, the noise consultants asked the airport'scommittee members to pick sites from maps. As recorded in the committeesminutes in 1999, (See, e.g.,http://sus.airportnetwork.com/Committees%20Meeting%2010-24-02.pdf.,incorporated herein by reference) noise consultant Paul Dunholter askedcommittee members to suggest areas for placement of noise monitors:

“Paul Dunholter, Project Acoustical Engineer, explained the purpose ofthe noise monitoring process. The primary tool for the noise analysis isthe integrated noise model which generates the noise contours. Themonitoring provides information to engineers about noise levelsgenerated by specific aircraft at specific locations that they can useto compare with the levels that model predicts. A network of noisemonitors will provide a noise pattern that will be combined with radardata from Lambert Field and FAA aircraft situational display data.Placing monitors at key technical locations and at places the communitychooses helps provide data to verify that the model will do a reasonablygood job of predicting noise levels. There will be around eight to tenmonitoring sites for continuous and five to six for spot measuring. Thelength of time will depend on weather conditions and mix of aircraft.Sideline noise is harder for the model to predict, so monitoring mayhelp provide data to improve contour accuracy. Exact monitoring timeswill not be widely publicized. The noise monitoring is in addition tothe FAA modeling requirements; the airport wants to obtain adequate datato verify that the model accurately predicts conditions around theairport. The model has been improved since the previous study. Besidesthe DNL contour, other metrics will be produced that will help the groupevaluate how various alternatives will impact noise levels. This studywill address aircraft associated with Spirit of St Louis Airport, notthose from Lambert or other airport. Regarding corporate jets, the newerplanes (Stage III) are dramatically quieter than the older models (StageII) which are gradually becoming a smaller percentage (now around 10%)of the fleet mix. Mr. Dunholter asked committee members to look at themap and suggest sites for placing monitoring equipment within generalareas. Several neighborhoods were identified and representatives askedto provide specific site proposal information.”

Highly accurate flight track information from multilateration, coupledwith detailed aircraft information, allows for accurate modeling ofnoise levels at any location. Coupling this with validation informationbased on several real time monitor locations allows for validatedestimates throughout a local area. Therefore it is now possible todeploy a small subset of monitors at locations of convenience and toaccurately model noise events from aircraft throughout an area aroundthe airport.

In a third embodiment, multilateration is used to perform noise monitorevent triggering based on real-time noise calculation and flighttracking. Triggering noise monitors acoustically is difficult in areasof high ambient or low source level noise. For example at the 129th ASAMeeting in Washington, D.C. in May 1995, Mr. Nathan B. Higbie gave apresentation on the subject as follows:

“The agreements negotiated for the new Denver Airport present aninteresting example of how legal considerations can govern how noisemeasurements are made. The agreements stipulate certain noise limits oncommunities surrounding the airport. These limits are expressed inaircraft Leq(24), and are placed at 102 points, some over 15 miles away.There are financial penalties if any values are exceeded for a year. Asignal-to-noise measurement problem resulted since modeled values of theaircraft Leq(24) were lower than measured Leq(24) community noise. Theproblems that needed solving were detection and quantification ofaircraft noise in low signal-to-noise, and assignment of each noiseevent to its source. Arrays and other spatial techniques were proposed,but were too costly and would not meet Type 1 measurement requirements.A floating threshold was implemented so that noise events could bedetected for any ambient condition. To date, all airport monitoringsystems have used a fixed threshold since signal-to-noise is not aproblem. The events are then correlated with the flight track data usinga statistical pattern recognition algorithm whose parameters areoptimized for each monitor location.”

Specifically, Mr. Higbie pointed out that the problems that neededsolving were detection and quantification of aircraft noise in lowsignal-to-noise, and assignment of each noise event to its source. Oneway to overcome this is to use a high fidelity multilateration flighttracking source which when integrated with the static monitors, willeffectively tell the monitors when and where to detect aircraft noiseevents. This a priori knowledge would assist in event detection beforethe monitors are able to detect the aircraft based on real time noisemeasurement and modeling. This technique works where other monitor-basedtriggering techniques cannot, and it has much higher capture rates thanconventional techniques. Works when signal levels are below noiselevels.

In this embodiment of the present invention, aircraft tracking data maybe used to trigger or “gate” local noise monitors, such that ambientnoise is ignored when aircraft are not present in an area covered by alocal noise monitoring device. When an aircraft track indicates it maybe in the proximity of a noise-monitoring sensor, data from that sensormay be monitored during that period only. In this manner, ambient noisefrom local conditions will not be mistaken for airplane noise.

Similarly, triggering may be used to measure ambient noise at a locationwhere no airplane noise is present. Determining the effect of airplanenoise on a particular environment requires that a measurement ofbackground or ambient noise be made, so that the effect of aircraftnoise in the area of measurement be determined. If an area is inherentlynoisy due to ambient conditions (e.g., truck traffic or the like), thenaircraft noise might not be deemed a nuisance. Abating aircraft noise insuch ambient noisy environments is a waste of noise operations resourcesand also unfair to aircraft owners and operators. Using multilaterationto track aircraft, it is possible to determine when a particular noisemonitor is not being affected by aircraft. At such instances,measurements of ambient or background noise can be correctly made sothat the overall effect of aircraft noise can be correctly evaluated.

In a fourth embodiment, multilateration may be used to support highlyaccurate correlation of aircraft flight tracks and aircraftidentification to noise levels. Some older style noise monitoringsystems had very limited flight tracking data, and some had none at all,meaning they could only really collect ambient noise levels over timewith little or no correlation to aircraft flight tracks and movements.In a press release dated Jan. 15, 2003, BridgeNet provided the followinginformation on a (then) new noise system at Jackson Hole Airport,Jackson Hole, Wyo. (www.airportnetwork.com, incorporated herein byreference):

“The Jackson Hole Airport Board, responsible for the Jackson HoleAirport (JAC), Teton County, Wyo., awarded the contract for theacquisition and installation of a permanent noise monitoring system(NMS) to BridgeNet International, based in Costa Mesa, Calif. Thisproject presents several unique challenges for an airport NMS. Theairport is located entirely within Grand Teton National Park, the onlyU.S. airport to have such a distinction. The pristine and sensitiveenvironment require that the system measure noise in remote and quietback country locations while blending in with the surroundingenvironment. BridgeNet International is utilizing noise-monitoringhardware manufactured by 01dB-Stell, (headquartered in Lyon, France) toprovide a system capable of meeting the goals and requirements of theNMS desired by the Jackson Hole Airport Board. The noise monitoringsystem is designed to operate remotely with only the noise monitoringhardware located in the airport environs. All analytical and reportingtools are accessed through the Internet using BridgeNet's web-basedtechnology. BridgeNet will provide the collection and analyticalsoftware tools allowing the airport to monitor, analyze and report thenoise environment created by aircraft operations. All collected data andsoftware will be located in BridgeNet's offices in California and can beaccessed by JAC Airport through the Internet. This remote accessibilityprovides JAC Airport administrators with all of the analytical andreporting tools necessary to monitor and model the noise environment,without the need for additional personnel and cost. BridgeNet continuesto pioneer the advantages of a “virtual noise office” by designingsystems capable of integrating disparate data and then transforming thisdata into useful information via web-accessible applications software.The installation of a permanent NMS comes after many years of seasonalnoise measurements and fulfills both the desires and requirements of theJAC Board to meet their obligations to the National Park Service and theDepartment of the Interior. Final installation will occur in summer of2003.”

Without an independent source of flight tracking that is independent ofground based Radar, airport noise offices such as Jackson Hole will havedifficulty correlating flight information to noise events, asground-based radar tracks are generally not available to noise officersin real-time. In order to properly identify noise events with particularaircraft, a noise officer needs unfettered access to tracking and noisedata to make correlations, or to have such correlations madeautomatically. Air Traffic Control radar data is generally availableonly through the use of tapes or removable disks, which have to berequested and analyzed, often days or weeks after an event. By contrast,other similar small airports with no nearby Radar contracted formultilateration-based noise and operations systems and do have thecapability to track and identify aircraft and performance manydifference noise office functions that rely on flight tracks. Theseairports include Hyannis, Mass., Cincinnati Lunken, Ohio, East Hampton,N.Y., Ohio State University, Ohio, and Hanscom, Mass.

Aircraft noise violations can thus be determined in real-time, either byusing measured noise data from noise monitoring systems, virtual noisecalculations, or a combination of both and other techniques. Aircraftcausing the noise violation can be identified in real-time. With thissystem, a pilot or other use can be notified in real-time of a noiseviolation, and effective action taken to alleviate or reduce the impactof the noise violation by reducing rate of climb, thrust, changingflight path, or other action. A pilot or other user may be notifiedusing verbal radio commands, recorded messages, visual display, or thelike.

Virtual noise calculation techniques can be used to warn when noiselevels are approaching violation thresholds, such that the pilot orother use can be warned of such an occurrence. Different colors may beused in a visual display (e.g., green, yellow, red) to indicate noiselevel violation status, with green meaning no violation, yellow meaninga violation threshold has been approached, and red meaning a violationhas occurred. Of course, the pilot retains ultimate authority over hisaircraft, and can ignore such warnings if conditions require (e.g.,emergency situation, weather conditions, or the like). In addition,virtual noise monitoring equipment can be aircraft-mounted, using rateof climb, thrust, load, and altitude data to calculate virtual noiselevels on the ground.

Such a predictive system sending noise warnings to the pilot may do soin such a way not to interfere with safety. A pilot shouldn't be makinga last minute evasive maneuver to avoid creating noise. However, thesystem may be programmed to advise the pilot that a if they areexecuting a particular standard arrival (STAR) or standard departure(SID) with a particular aircraft configuration and weight, and the like,that such conditions may or will cause a noise violation. Obviously,safety is paramount, and it would be necessary not to add to cockpitclutter and/or distract the pilot with noise data during sensitivetakeoff and landing operations, unless such data could be presented inan unobtrusive manner and/or provided during pre-flight or non-sensitiveflight times.

In a fifth embodiment, high fidelity aircraft dynamics frommultilateration data is used to support new generation airport websitesand provide unique website features. At the time of filing the presentapplication, the WebScene™ website, powered by AirScene™ multilaterationflight tracking, is poised to become the leading website for airportNOMS, with clients including Providence R.I., San Antonio Tex.,Louisville Ky., Ohio State University, Ohio, Indianapolis, Ind., Boston,Mass., and Raleigh-Durham, N.C.

Examples of traditional-style websites include San FranciscoInternational Airport shown at http://www.flyquietsfo.com/live/,incorporated herein by reference. That website uses near-real-timetracking of aircraft using their Mode A/C codes (not Mode S) andtherefore was unable to identify specific aircraft in near-real-time, asis illustrated in the example display of FIG. 8, where all of theaircraft identification fields are blank.

Other airport websites have used a timed delay of Government radar suchas: http://www.oaklandtracks.com/noise/noise_management_replay.html,also incorporated herein by reference. This particular style of websiterequires the viewer to install an SVG plug-in before viewing. The flighttracks use delayed data from FAA Radars, and the noise levels are actualrecorded levels as fixed noise monitor locations. Although plugs-in arerequired and the data are delayed in cooperation with the FAA, thisstyle of website was quite progressive when it was introduced circa2003. FIG. 9 shows an example of a web page display from that website.

In early 2005, Rannoch Corporation introduced a “2nd generation” websitefor airport noise and operations monitoring. This advancement offers astate-of-the-art noise monitoring system with a fully-integrated websolution. For some airports, the Web interface to AirScene™ is theprimary method through which many airport employees and for mostcommunity users to experience the NOMS. In designing the interface itwas vital that it be straightforward, intuitive, and secure. Rannochalso offers on-site fully-integrated approaches to websites in order toprovide the highest levels of access, simplicity, functionality,flexibility, data security, and data consistency.

One of the primary functions of the website is to interactively displayflight tracks on a base map. To accomplish this objective, Rannoch's webdisplay design has an interactive map that has the capability displaynear-real-time and historical operations, tracks, and available noisedata. A user may select a flight operation in order to; display flightnumber, aircraft ID, beacon code, “current” altitude and speed; initiatea complaint from the operation; perform an “is it normal” assessment ofthe operation based on criteria defined by the airport; zoom in and out,pan, re-center, and control playback speed; and zoom the map to aspecific street address as part of an address lookup function.

The user community may also be able to submit complaints to the airportthrough the web interface. To accomplish this task, Rannoch'ssecond-generation web solution provides an interactive complaint entryform for the users to enter critical information about the complaint.This form contains the following basic features: a complaint entry formand web entry form; complaint entry functionality that assures thatcomplaint data are entered into the AirScene™ complaint database tomaintain data continuity; and the capability to allow the user to entercomplains either anonymously or as a registered user. For registeredusers, the system may provide: a secure login capability, and theability to check the status of their complaints and receive status viaemail. The email response will be similar in form and content to the“Aircraft Disturbance Report”.

Rannoch's web solution also allows the user to view reports. Some of thereports include runway utilization, property look-up, and noisecontours. In addition, the user is able to run a subset of reportsinteractively on the website, facilitating user-driven analysis andinformation gathering on disturbances. Rannoch's 2^(nd) generation websolution is more seamless and secure than earlier predecessors. Itreduces the need for browser plug-ins that the end user would need toinstall on their computer. Instead of re-directing the browser tooutside URLs, the website can be hosted by the airport. Browsers cangain access to the data through Port 80 making use and support of thewebsite simpler. This solution allows the airport to better controlaccess, security to the data, and improve overall performance.

In a sixth embodiment, the use of multilateration flight trackingenables real-time modeling of aircraft noise levels throughout anairport's terminal area. This embodiment enables new features, whichallow high-fidelity calculations of aircraft-generated noisesubstantially at any point in space around an airport. Virtual NoiseMonitor (VNM) is a component of the next generation airscene.netplatform.

Virtual Noise Monitoring makes use of the integration and fusion of datafrom multiple sources such as ACARS, D-ATIS and Rannoch's own highprecision AirScene™ multilateration and ADS-B surveillance technologies,which provide the most complete, accurate, and real-time information onaircraft location and movement. Without denying the value of traditionalnoise measuring equipment, the inclusion of this extra information intohigh-power, user-friendly applications, which incorporate both existingand innovative modeling solutions, will allow airports to providenoise-monitor-equivalent output at any point in the community—on demand.Aircraft noise and emissions calculations had previously been greatlydependent on a variety of modeling assumptions and on a level ofprofessional judgment that placed a practical limit on the accuracy andrepeatability of the analysis. With billions of dollars of propertydevelopment, noise insulation programs, and land acquisition activitiesriding on the calculation of the noise levels worldwide, the VirtualNoise Modeling of the present invention raises the industry standard fornoise model accuracy.

The VNM process uses a number of techniques for improving thecalculation of noise metrics based on data available only in AirScene™,including high-resolution flight track data from the ADS-B andmultilateration flight tracking systems; actual aircraft weight, type,engine type and thrust; and a variety of weather and environmentalinformation. More accurate modeling may help answer questions associatedwith questionable results from physical noise monitors located in areaswhere high ambient levels, other intrusive sources, and multiplesimultaneous noise events prevent accurate measurements. AirScene™features improve the accuracy of current modeling techniques by greatlyimproving the quality of the input data, especially flight track data.Since airports worldwide are becoming more dependent on noise modelingto direct large investments in residential insulation and propertyacquisition, the next logical step is to increase the accuracy of themodeling input.

FIG. 10 is a block diagram illustrating the relationship betweendifferent embodiments of the present invention. As illustrated in FIG.10, data from the various embodiments may be displayed on computer 1000which may comprise a personal computer, workstation, or the like,connected directly to an AirScene™ system, or coupled though theinternet or other network, which may display relevant data as a websiteor the like.

Such a website may comprise, for example, the AirScene™ Airport NoiseOperations Monitoring (NOMS) website 1010 as illustrated in FIG. 10.NOMS website 1010 may display real-time aircraft flight track displaydata from a passive flight tracking system, such as the Rannoch™AirScene™ multilateration system. From this accurate flight track dataand from noise generation models, predicted noise levels from “virtual”noise monitor locations may be generated. These may be displayed alongwith noise levels from actual physical noise monitors, and the valuescompared to validate the noise models, and also indicate the validity ofphysical noise monitors.

As noted above and in earlier applications, flight track data fromaircraft 1090 may be obtained by multilateration of radio signals fromaircraft 1090. These radio signals may be received at a number of radioreceivers 1030, which may be located at the airport 1070 or nearby. Inone embodiment, receivers 1030 are located on shared wirelesscommunication towers (e.g., cell phone antenna sites) or other readilyaccessible locations, and may be packaged with other monitors such asnoise, emissions, and other environmental monitors (e.g., temperature,humidity, wind velocity and direction, wind shear, and the like). Theaccurate aircraft track produced through multilateration enhances theaccuracy of existing and proposed virtual noise models. Moreover, theuse of off-site radio receivers 1030 allows the system to operateindependently from airport 1070.

Custom data reports may also be provided on website 1010 and complaininput forms (either as on-line data entry or downloadable forms) may beprovided via secure user login. Providing a user login with name andaddress and password data would prevent overly zealous noise complaintusers from spoofing the system by providing false complaint data (e.g.,entering a neighbor's name and address on a complaint form to make itappear that more people are complaining than actually are). Complaintdata can be manually or automatically audited by e-mailing, calling, ormailing selected users to confirm whether their complaint was actuallymade.

Public and private data may be made selectively available to enableusers to track complaint status on-line, see responses to submittedcomplaints, enter new complaints, and customize their own userenvironment (myAirScene™). Privacy concerns may be addressed byproviding data selectively to users such that personal identificationinformation (name, address, and the like) is available on a selectedbasis to system operators. Public users can monitor their own complaintdata and may be allowed to view complaint data from others with personalinformation suitably redacted.

In another embodiment of the present invention, aircraft emissionsexceedance warnings 1020 may be generated by the system. Real timetracking data, combined with a predictive modeling 1040, may notify auser and pilot when emissions from the aircraft may exceed predeterminedguidelines. Again, from aircraft track, weight, engine type, and otherdata, aircraft emissions modeling may predict emissions using a virtualmodel based upon these inputs. This emissions warning may be audio orvisual, and can be transmitted to the pilot in real-time. Such warningscan reduce the amount of airport emissions and thus help cities andother jurisdictions comply with clean air law requirements.

In addition, aircraft emissions modeling 1040 may be used to determineoverall aircraft emissions from an airport, and calculate aircraftemissions over time. From such data, and airport operator can determinewhether aircraft emissions are increasing or decreasing over time, andalso determine what events are causing increased emissions. For example,if larger numbers of older, more polluting aircraft are the cause ofincreased emissions, an airport operator can work with airlines toschedule newer aircraft for routes to that airport. Alternately, landingfees can be evaluated and adjusted based upon emissions levels ofaircraft involved, to provide an incentive for airlines to use loweremissions aircraft and/or train pilots to avoid high emissions producingmaneuvers. Similarly, if it is determined that certain maneuvers areresulting in increased emissions, airport operators can study operationsand determine whether standard approaches, runway use, or the like, canbe modified to reduce emissions levels. In addition, idling and taxiingtime may be monitored to determine whether such activities arecontributing to airport emissions. There are number of different usesfor such data, and only a few are enumerated here by way of exampleonly. Overall emissions data may be used to comply with Federal cleanair law requirements.

Note that these additional embodiments do not require a substantialadditional investment in additional equipment. Aircraft emissions can bevirtually calculated, which may be validated by actual emissionsmeasurements by physical monitors packaged with receiver 1030 or atother locations. Thus, plurality of functional features may be providedusing the same underlying hardware. Note also that in an additionalembodiment of the present invention, multilateration tracking softwaremay be used to locate the optimal placement for noise monitoringstations, based upon typical aircraft tracks or the like. Additionalnoise monitoring stations may be located at other shared wirelesscommunication towers or other locations as required to accurately trackthe bulk of aircraft, based upon cumulative tracking data produced bythe multilateration system of the present invention.

Actual aircraft emissions measurements 1050 may also be made to validatevirtual emissions modeling 1040 and to provide the same warnings andairport operations options offered by virtual emissions modeling 1040. Acombined sensor package, or individual emission sensors, may transmitemissions data to the AirScene™ database, where it may be fused withaircraft tracking data to generate actual emissions reports, and/orvalidate or supplement virtual emissions modeling.

In addition to the other features described above, the use ofmultilateration tracking allows for what is known as sensor situationalawareness 760. As noted previously, Prior Art noise level monitoring wasrather primitive, with little more than microphones being placed in thecommunity. Prior Art emissions monitoring was not much moresophisticated. The problem with such plug-and-monitor approaches is thatambient noise, noise from other than aircraft sources, and sensor errorcould cause false data readings. The same is true for emissionsmodeling. If a loud, smoke-belching construction truck is operating nextto a noise and/or emissions monitor, the monitors may report noise andemissions levels, which are unrelated to aircraft operations.

Since the present invention “knows” when there is an aircraft overheador in the vicinity (via multilateration tracking) the system can cutoffemissions and/or noise measurements during periods when no aircraft arepresent in the vicinity. Thus, false positives in reporting data areeliminated. In addition, since the system also “knows” that there are noaircraft overhead or in the vicinity, noise and/or emissions monitorscan take background or ambient measurements. Such data may prove (ordisprove) whether aircraft are indeed a substantial cause of urbanpollution (noise or emissions). If the effect of aircraft isdemonstrated to be negligible, then resources for reducing noise andemissions can be redirected to other, more prominent sources. Ifaircraft, or certain aircraft or flight patterns are shown to be a causeof significant emissions or noise, then actions can be taken to reducesuch problems. Whether aircraft are a significant source of noise andemissions, and how different aircraft and flight path affect theseparameters is nearly impossible to determine without accuratemeasurement and modeling data. The present invention provides this soliddata, which will allow airport operators to make more informed andeffective decisions.

While the preferred embodiment and various alternative embodiments ofthe invention have been disclosed and described in detail herein, it maybe apparent to those skilled in the art that various changes in form anddetail may be made therein without departing from the spirit and scopethereof.

1. A method of performing real-time calculation of virtual noise levelscaused by aircraft, comprising the steps of: receiving, at a pluralityof locations, radio signals from the aircraft; time-stamping receivedradio signals from the aircraft with a time value indicating a time aradio signal is received at one of the plurality of locations;calculating aircraft position and track from time stamps from theplurality of locations; identifying the aircraft from data in the radiosignals; and determining noise levels generated by the aircraft, fromaircraft position and track in real time and outputting aircraft noiselevel data.
 2. The method of claim 1, wherein the plurality of locationsincludes at least one shared wireless communication tower.
 3. The methodof claim 1, further comprising the steps of: storing aircraft position,identification, and track data and noise level data in a database;receiving an aircraft noise query from a user; searching the database;and outputting at least one of aircraft identification information,aircraft position information, aircraft track information and noiselevel data in response to the aircraft noise query.
 4. The method ofclaim 1, further comprising the steps of storing aircraft position,identification, and track data and noise level data in a database;displaying, on a website, in at least one of real-time or delayed, atleast one of aircraft identification information, aircraft positioninformation, aircraft track information and noise level data.
 5. Themethod of claim 4, further comprising the steps of: receiving, from auser of the website, noise complaint data including at least one of userlocation, user name, and time of complaint.
 6. The method of claim 1,wherein the step of determining noise levels comprises the step ofvirtually determining noise levels using a predetermined algorithm basedupon at least aircraft track, and one or more of aircraft type, aircraftweight, and engine type.
 7. The method of claim 6, further comprisingthe steps of: measuring aircraft noise using at least one physical noisemonitor to measure actual aircraft noise at a predetermined location,and comparing measured aircraft noise with virtually determined noiselevels to validate the predetermined algorithm.
 8. The method of claim7, wherein the at least one physical noise monitor is located at ashared wireless communication tower.
 9. The method of claim 8, whereinat least one of the plurality of locations is the shared wirelesscommunication tower.
 10. A method of performing real-time calculation ofvirtual emission levels caused by aircraft, comprising the steps of:receiving, at a plurality of locations, radio signals from the aircraft;time-stamping received radio signals from the aircraft with a time valueindicating a time a radio signal is received at one of the plurality oflocations; calculating aircraft position and track from time stamps fromthe plurality of locations; identifying the aircraft from data in theradio signals; and determining emissions levels generated by theaircraft, from aircraft position and track in real time and outputtingaircraft emissions level data.
 11. The method of claim 10, wherein atleast one of the plurality of locations is a shared wirelesscommunication tower.
 12. The method of claim 10, further comprising thestep of providing at least one of a real-time or delayed display ofaircraft tracks and emission levels on an internet website.
 13. Themethod of claim 10, wherein the step of determining virtual emissionslevels comprises the step of determining emissions levels using apredetermined algorithm based upon at least aircraft track, and one ormore of aircraft type, aircraft weight, and engine type.
 14. The methodof claim 13 further comprising the steps of: measuring aircraftemissions levels using at least one physical emissions monitor tomeasure actual aircraft emissions at a predetermined location, andcomparing measured aircraft emissions with virtually determinedemissions levels to validate the predetermined algorithm.
 15. The methodof claim 14, wherein the at least one physical emissions monitor islocated at a shared wireless communication tower.
 16. The method ofclaim 15, wherein at least one of the plurality of locations is theshared wireless communication tower.
 17. A method of measuring aircraftnoise, comprising the steps of: determining at least one aircraft flighttrack using multilateration of radio signals generated by at least oneaircraft; measuring at least one noise metrics, including one or more ofsingle event level (SEL), maximum level (Lmax), noise level profile(noise level vs. time), effective perceived noise level (EPNL),perceived noise level with tone weighting (PNLT), and EquivalentContinuous Noise Level (Leq). Correlating the at least one noise metricwith the at least one flight track to identify the aircraftcorresponding to the at least one noise metric.
 18. A method ofmeasuring aircraft noise, comprising the steps of: determining inreal-time, at least one aircraft flight track using multilateraion ofradio signals generate by at least one aircraft; determining, from theat least one aircraft flight track, when an individual physical noisemonitor is exposed to no aircraft noise; and measuring noise levels atthe individual physical noise monitor.
 19. The method of claim 18,further comprising the step of: measuring true ambient noise at theindividual physical noise monitor when no aircraft noise is present tocorrupt measurement conditions.
 20. The method of claim 19, furthercomprising the steps of: determining from the at least one flight track,when an aircraft is within the vicinity of the individual physical noisemonitor; and comparing noise levels when the aircraft is within thevicinity of the individual physical noise monitor with the measured trueambient measurement data to allow extraction of low-level aircraft noiseevents from actual noise data measured by the individual physical noisemonitor.
 21. The method of claim 20, wherein the individual physicalnoise monitor is located at a shared wireless communication tower. 22.The method of claim 21, wherein a multilateration sensor for determiningflight track is located at the shared wireless communication tower. 23.A system for monitoring environmental conditions and environmentalimpact of vehicles, including at least one of noise and emissions levelsof the vehicles, the system including: a plurality of receiver packageslocated at a plurality of locations, the receivers including a radioreceiver, and at least one of a physical noise monitor and a physicalemissions monitor; and a processing station, coupled to the plurality ofreceiver packages, the processing station receiving time-stamped signalsfrom the radio receiver and determining track of a vehicle bymultilateration of the time-stamped signals, the processing stationcalculating at least one of virtual noise levels based in part upon thevehicle track, virtual emissions levels based in part upon the vehicletrack, measured noise levels from a physical noise monitor, and measuredemissions levels from a physical emissions monitor.